Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which wireless communication devices (WCDs) (also known as user equipment devices (UEs)), such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a WCD within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other WCDs served by the base station.
In general, a cellular wireless network may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to WCDs defining a downlink or forward link and communications from the WCDs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Wireless Interoperability for Microwave Access (WiMAX), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of WCDs, initiation of communications, handoff between coverage areas, and other functions.
In accordance with the air interface protocol, each coverage area may operate on particular frequency spectrum in the form of one or more ranges of radio frequency (RF) spectrum defining a frequency bandwidth of the coverage area. Depending on the air interface protocol, the coverage area may use different spectrum for its uplink and downlink or may use the same spectrum allocated over time or in another manner between its uplink and downlink. Further, various coverage areas of the network could use the same frequency spectrum as each other, with communications in adjacent coverage areas being modulated or otherwise encoded to distinguish one coverage area from another.
In each coverage area, the air interface may then be divided into a plurality of “resource blocks” for carrying communications wirelessly between the WCDs and the base station. These resource blocks may take various forms, depending on the air interface protocol. For instance, in a representative LTE system, the air interface may be divided over time into 0.5 millisecond timeslots, and in each timeslot the bandwidth of the coverage area may be divided into resource blocks each spanning 180 kHz. Thus, every 0.5 milliseconds, the air interface would define a number of 180 kHz resource blocks that would fit within the available bandwidth.
Further, the air interface may define various channels for communication between the WCDs and the base station. For instance, on the downlink, the air interface may define a pilot or reference channel on which the base station broadcast a signal that WCDs may monitor to evaluate coverage strength, a downlink control channel for carrying control signals from the base station to WCDs, and one or more downlink traffic channels for carrying communication traffic to WCDs And on the uplink, the air interface may define an uplink control channel for carrying control signals from WCDs to the base station, and one or more uplink traffic channels for carrying communication traffic from WCDs. These various channels may be defined in particular resource blocks or portions of resource blocks and/or may define or be divided into the resource blocks.
When a WCD first powers on or enters into coverage of a base station, the WCD may scan for and identify a strongest pilot or reference signal and may register with the network by transmitting a registration request or attach request to a base station providing that signal. This registration process may serve to notify the network of the WCD's presence in that base station's coverage area and to facilitate network authentication of the WCD. Once registered, the WCD may then be served by the base station in an idle mode or a connected (active) mode. In the idle mode, the WCD may generally monitor a downlink control channel for any page messages or other overhead information from the base station. And in the connected mode, the WCD may have an established radio link connection with the base station, through which to engage in communication of bearer data (e.g., user communication traffic) with the base station.
When a WCD is served in a connected mode by a particular base station, the base station (alone or with the assistance of associated network infrastructure) may manage assignment of resource blocks for use to carry communication traffic between the base station and the WCD. For instance, when a WCD has data to communicate on the Internet, the WCD may transmit to the base station a service request message informing the base station that the WCD has data to communicate, and the base station may then assign one or more upcoming resource blocks on the uplink for use by the WCD to transmit that data and may send to the WCD a control signal specifying the assigned resource block(s). The WCD may then transmit its data to the base station in the assigned resource block(s), and the base station may forward the data for transmission on the Internet. Likewise, when the base station has data to transmit to the WCD, the base station may assign one or more upcoming resource blocks on the downlink for use to carry that data and may send to the WCD a control signal specifying the assigned resource block(s), and the base station may transmit the data to the WCD in the assigned resource block(s).